package features.advance.leetcode.linkedlist.easy;

import features.advance.leetcode.geometry.doublepointer.easy.ListNode;
import features.advance.leetcode.util.TreeUtil;

/**
 * 剑指 Offer 25. 合并两个排序的链表
 *
 * 难度：简单
 *
 * 输入两个递增排序的链表，合并这两个链表并使新链表中的节点仍然是递增排序的。
 *
 * 示例1：
 *
 * 输入：1->2->4, 1->3->4
 * 输出：1->1->2->3->4->4
 * 限制：
 *
 * 0 <= 链表长度 <= 1000
 *
 * 注意：本题与主站 21 题相同：https://leetcode-cn.com/problems/merge-two-sorted-lists/
 *
 * @author LIN
 * @date 2021-06-23
 */
public class Offer25 {

    public static void main(String[] args) {
        Solution solution = new Solution() {
        };

        ListNode l1 = TreeUtil.parseLinkedList("[1,2,4]");
        ListNode l2 = TreeUtil.parseLinkedList("[1,3,4,6]");
        ListNode listNode = solution.mergeTwoLists(l1, l2);
        System.out.println(listNode);


    }

    static class Solution {
        /**
         *  虚拟头
         * @param l1
         * @param l2
         * @return
         */
        public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
            ListNode h = new ListNode(0);
            ListNode cur = h;
            while (l1 != null && l2 != null){
                if(l1.val > l2.val){
                    cur.next = l2;
                    l2 = l2.next;
                }else{
                    cur.next = l1;
                    l1 = l1.next;
                }
                cur = cur.next;
            }
            cur.next = l1!=null?l1:l2;
            return h.next;
        }
    }
}
